Motion analyzing apparatus, motion analyzing method, and motion analyzing program

ABSTRACT

When a sporting tool or a subject changes from a first state (e.g., address state) to a second state (during swing), a detection part detects, within a plane orthogonal to a first direction (y-axis) in which a shaft part of the sporting tool extends, a rotation angle θxn or θzn at which the sporting tool or the subject changes around an axis in a second direction or a third direction orthogonal to each other (x-axis or z-axis) using output of an inertial sensor.

CROSS REFERENCE

The entire disclose of Japanese Patent Application No. 2013-226036, filed Oct. 30, 2013, is expressly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a motion analyzing apparatus, a motion analyzing method, a motion analyzing program, etc.

2. Related Art

A motion analyzing apparatus is used for analysis of motion including swing motion. At swing, a sporting tool is swung. At swing, the grip of the sporting tool is held by hands of a user. When the sporting tool is swung, the position of the sporting tool changes according to the time axis. An inertial sensor is attached to the sporting tool. The swing motion is visually reproduced based on the output of the inertial sensor. As one specific example of the motion analyzing apparatus, for example, a golf swing analyzing apparatus disclosed in Patent Document 1 (JP-A-2008-73210) is cited.

For example, golf swing starts from address, take-back, halfway-back, top, through down-swing and impact, follow-through, to finish. At the start of the golf swing, a subject determines the position of a golf club at impact in advance at address. As a result, the direction of the face of the club head is set. If the direction of the face at address is reliably reproduced at impact, the hit ball flies as expected. However, actually, it may be impossible to hold the same direction of the face at impact as that at address as expected. Accordingly, it is necessary to indicate comparisons between rotation angles of the shaft part of the golf club and the directions of the face angles of the club head at address and at impact for the subject. If an optical motion capture system in which a plurality of cameras or the like is used, the face angles of the hit surface of the golf club at address and at impact maybe imaged and the directions of the face angles may be specified from images, however, the system is inconvenient due to the large-scaled system, difficulty in installation outdoors, etc.

SUMMARY

According to at least one aspect of the invention, a motion analyzing apparatus and a motion analyzing program that can easily present rotations of a sporting tool or arms and wrists of a subject as one index for motion analysis may be provided.

(1) An aspect of the invention relates to a motion analyzing apparatus including an arithmetic processing circuit that calculates, within a plane orthogonal to a first direction in which a shaft part of a sporting tool extends, a rotation angle changing around an axis in at least one of a second direction and a third direction orthogonal to each other based on an inertial force generated when a first state changes to a second state by swing motion.

The sporting tool is held with hands and the sporting tool is swung at swing. At swing, the position of the sporting tool changes according to a time axis. For starting swing, a subject determines the position of the sporting tool at impact in advance. From here, swing motion including impact is newly performed. In the aspect of the invention, for example, a rotation angle of the sporting tool around a predetermined axis between address (first state) to the second state in a certain location during swing, a relative rotation angle changing between the first state and the second state during swing, etc. are detected. By visual representation of the rotation angles on a screen of a display device based on image data, within the plane orthogonal to the first direction in which the shaft part of the sporting tool extends, at least one of rotations of the sporting tool and the wrist and the arm of the subject around the axis in the second direction and the third direction orthogonal to each other may be presented to the subject. As the rotation of the sporting tool, in golf as an example, it is known that, not only the rotation around the axis in the first direction in which the shaft part extends (shaft rotation) but also cock and arm rotation as rotations of the wrist around axes extending in the second and third directions intersecting with the shaft part have an effect on the direction of the hit ball after impact. The subject may improve the form of swing in response to the presented rotations around the axes intersecting with the shaft part. Further, in comparison with optical motion capture using a plurality of cameras, the rotation angles around the axes intersecting with the shaft part of the sporting tool may be measured only by attachment of the inertial sensor to the sporting tool. Thus, there are such advantages that the measurement may be easily performed and the apparatus can be used in any place, even outdoors.

(2) In one aspect of the invention, the first state is a state before start of the swing motion and the second state is a dynamic state of the swing motion. During swing motion, the rotation angles between address and a certain location during swing is detected around the axes intersecting with the shaft part of the sporting tool. By visual representation of the rotation angles on the screen of the display device based on image data, rotations around the axes intersecting with the shaft part of the sporting tool may be presented to the subject.

(3) In one aspect of the invention, the second direction is along a rotation axis at pronation or supination of a wrist of the subject holding a grip part of the sporting tool. In this case, in golf as an example, the detection part may detect the rotation angle of the arm rotation in which the back of the right wrist is directed upward or downward by the rotation (pronation or supination of the wrist).

(4) In one aspect of the invention, the third direction is along a rotation axis at ulnar flexion or radial flexion of a wrist of the subject holding a grip part of the sporting tool. In this case, in golf as an example, the detection part may detect the rotation angle of the cock of the wrist at take-back (ulnar flexion or radial flexion of the wrist) and the reverse rotation angle of the wrist near impact.

(5) In one aspect of the invention, the arithmetic processing circuit calculates a relative value of the rotation angle changing around the axis in the first direction between the first state and the second state. In this case, in golf as an example, the detection part may further detect the rotation angle of the rotation generated around the axis in the direction in which the shaft of a club extends between the stationary state (first state) and the second state during swing motion (referred to as “shaft rotation” in the specification), for example.

(6) In one aspect of the invention, the motion analyzing apparatus outputs information of the rotation angle. For example, by representation of the rotation angle around the axis of the shaft part of the sporting tool at address and at impact, the apparatus may be utilized by the subject as a tool that promotes progress.

(7) In one aspect of the invention, a change of the rotation angle is output in response to a time during swing motion of the sporting tool. By displaying such information, the change of the relative rotation angle changing from the first state to the second state is visually presented in response to the time during the swing motion, and thereby, the subject can intuitively recognize the degree of change and the speed of change. According to the recognition, the subject may improve the form of swing.

(8) In one aspect of the invention, the information of the rotation angle is output with information of another rotation angle for comparison. By displaying such information, for example, in the case of golf swing, the swing motion of the subject and a swing motion of a professional and swing motion of another subject having equal skill to the subject may be displayed in comparison. According to the comparison, the subject may improve the form of swing.

(9) In one aspect of the invention, the motion analyzing apparatus includes an event detection part that specifies an event during swing motion based on the inertial force, and information of the rotation angle is correlated with the event. From impact, back-swing, top, down-swing, etc., several events occur during swing motion. When the rotation angle is specified with respect to each event, the subject may easily improve the form of swing.

(10) In one aspect of the invention, the motion analyzing apparatus outputs the event and the information of the rotation angle. By displaying such information, the rotation angle is visually presented with respect to each event, and thereby, the subject can intuitively recognize the relation between the rotation angle and the event. On the basis of the recognition, the subject may improve the form of swing.

(11) In one aspect of the invention, the event is output with information of another rotation angle for comparison. By displaying such information, the swing motion of the subject and the swing motion of a professional and the swing motion of another subject having equal skill to the subject may be displayed in comparison. Thus, the rotation angle of the subject can be compared with the rotation angle of the professional with respect to each event. According to the comparison, the subject may improve the form of swing.

(12) Another aspect of the invention relates to a motion analyzing method including calculating, within a plane orthogonal to a first direction in which a shaft part of a sporting tool extends, a rotation angle changing around an axis in at least one of a second direction and a third direction orthogonal to each other based on an inertial force generated when a first state changes to a second state by swing motion.

(13) Still another aspect of the invention relates to a motion analyzing program allowing a computer to execute a procedure of calculating, within a plane orthogonal to a first direction in which a shaft part of a sporting tool extends, a rotation angle changing around an axis in at least one of a second direction and a third direction orthogonal to each other based on an inertial force generated when a first state changes to a second state by swing motion.

The motion analyzing program may allow a computer to execute an operation of the motion analyzing apparatus according to the aspect of the invention. The program may be initially stored in the motion analyzing apparatus, stored in a memory medium and installed in the motion analyzing apparatus, or downloaded from a server through a network to a communication terminal of the motion analyzing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a conceptual diagram schematically showing a configuration of a golf swing analyzing apparatus according to one embodiment of the invention.

FIGS. 2A to 2C are diagrams for explanation of rotation angles θx, θy, θz around respective x, y, z axes.

FIG. 3 is a diagram for explanation of the rotation angle θx in FIG. 2A as a rotation angle of cock, uncock at which wrists are rotated toward a thumb side or little finger side.

FIG. 4 is a diagram for explanation of the rotation angle θZ in FIG. 2B as a rotation angle of hinge or its reverse motion at which the wrists are rotated toward a back side or palm side.

FIG. 5 is a conceptual diagram schematically showing relations among a motion analysis model, a golfer, and a golf club.

FIG. 6 is a block diagram schematically showing a configuration of an arithmetic processing circuit according to one embodiment.

FIG. 7 shows one specific example of an image visually representing a movement path of the golf club.

FIG. 8 shows one specific example of a graph showing changes of rotation angles according to a time axis.

FIG. 9 shows another one specific example of the graph showing changes of rotation angles according to the time axis.

FIG. 10 shows one specific example with additional comparison data to the graph showing changes of rotation angles according to the time axis.

FIG. 11 shows one specific example of a pseudo circular graph that correlates events with rotation angles around an x-axis.

FIG. 12 shows one specific example of a pseudo circular graph that correlates events with rotation angles around the x-axis.

FIG. 13 shows one specific example of a pseudo circular graph that correlates events with rotation angles around a y-axis.

FIG. 14 shows another specific example with additional comparison data to the pseudo circular graph that correlates events with rotation angles around the y-axis.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

As below, one embodiment of the invention will be explained with reference to the accompanying drawings. The embodiment to be described as below does not unduly limit the invention described in the appended claims, and all of the configurations explained in the embodiment are not essential as resolving means of the invention.

1. Configuration of Golf Swing Analyzing Apparatus

FIG. 1 schematically shows a configuration of a golf swing analyzing apparatus (motion analyzing apparatus) 11 according to one embodiment of the invention. The golf swing analyzing apparatus 11 includes, e.g., an inertial sensor 12. For example, an acceleration sensor and a gyro sensor are incorporated in the inertial sensor 12. The acceleration sensor can detect accelerations individually in three axes x, y, z orthogonal to one another. The gyro sensor can detect angular velocities individually around the respective three axes x, y, z directions orthogonal to one another. The inertial sensor 12 outputs detection signals. The acceleration and the angular velocity are specified with respect to each axis by the detection signals. The acceleration sensor and the gyro sensor detect information of the accelerations and the angular velocities relatively accurately.

The inertial sensor 12 is attached to a golf club (sporting tool) 13. The golf club 13 has a shaft 13 a and a grip 13 b. The grip 13 b is held by hands of a user. The grip 13 b is coaxially formed with the axis of the shaft 13 a. A club head 13 c is coupled to the end of the shaft 13 a. Desirably, the inertial sensor 12 is attached to the shaft 13 a or the grip 13 b of the golf club 13. It is only necessary that the inertial sensor 12 is relatively immovably fixed to the golf club 13.

Here, when the local coordinate system of the inertial sensor 12 with x, y, z is set for attachment of the inertial sensor 12, for example, the y-axis is set in a first direction in parallel to the longitudinal axis of the shaft 13 a. For example, the x-axis as another one of the detection axes of the inertial sensor 12 is set in a second direction in parallel to a target direction A intersecting with a face plane of the club head 13 c. For example, the z-axis as another one of the detection axes of the inertial sensor 12 is set in a third direction orthogonal to the x-axis and the y-axis.

FIGS. 2A to 2C, 3, and 4 are diagrams for explanation of rotation angles detected by the output from the gyro sensor of the inertial sensor 12. FIG. 2A is the diagram of the golf club 13 at address as seen from a direction in parallel to the target direction A (FIG. 1). Regarding a rotation angle θx at which the wrists are rotated around the x-axis in parallel to the target direction A (FIG. 1), in the case of golf, as shown in FIG. 3, a B1-direction in which the wrists are rotated to the thumb side indicates a radial flexion direction and a B2-direction in which the wrists are rotated to the little finger side indicates an ulnar flexion direction.

FIG. 2B shows a rotation angle θz around the z-axis. Regarding the rotation angle θz at which the wrists are rotated around the z-axis orthogonal to the x-axis, y-axis within a plane along a face 13 c 1 of the club head 13 c, in the case of golf, as shown in FIG. 4, a C1-direction in which the right wrist is rotated to the back side of the right hand indicates pronation at take back (back swing) and a C2-direction in which the right wrist is rotated to the palm side indicates supination at down swing to follow swing.

FIG. 2C shows a rotation angle θy around the y-axis. Regarding the rotation angle θy of the arms around the y-axis in parallel to the rotation angle of the shaft 13 a, in the case of golf, as shown in FIG. 2C, a D1-direction indicates a rotation angle generated around the longitudinal axis of the shaft (shaft rotation) at take-back (back-swing) and a D2-direction indicates a reverse rotation angle at which the rotation angle of the shaft is reversed (shaft rotation) at down-swing to follow-through.

The golf swing analyzing apparatus 11 includes an arithmetic processing circuit 14. The inertial sensor 12 is connected to the arithmetic processing circuit 14. For connection, a predetermined interface circuit 15 is connected to the arithmetic processing circuit 14. The interface circuit 15 may be in wired or wireless connection to the inertial sensor 12. The detection signals are supplied from the inertial sensor 12 to the arithmetic processing circuit 14.

A memory deice 16 is connected to the arithmetic processing circuit 14. For example, a golf swing analysis software program (motion analyzing program) 17 and relevant data may be stored in the memory device 16. The arithmetic processing circuit 14 executes the golf swing analysis software program 17 to realize a golf swing analyzing method. The memory device 16 may include a DRAM (dynamic random access memory), a mass-storage unit, an nonvolatile memory, etc. For example, the golf swing analysis software program 17 is temporarily held in the DRAM for implementation of the golf swing analyzing method. The golf swing analysis software program 17 and the data are saved in the mass-storage unit such as a hard disc drive (HDD). Programs and data having relatively low capacity such as BIOS (basic input/output system) are stored in the nonvolatile memory.

An image processing circuit 18 is connected to the arithmetic processing circuit 14. The arithmetic processing circuit 14 sends predetermined image data to the image processing circuit 18. A display device 19 is connected to the image processing circuit 18. For connection, a predetermined interface circuit (not shown) is connected to the image processing circuit 18. The image processing circuit 18 sends image signals to the display device 19 in response to the input image data. Images specified by the image signals are displayed on the screen of the display device 19. A liquid crystal display or another flat panel display is used for the display device 19. Here, the arithmetic processing circuit 14, the memory device 16, and the image processing circuit 18 are provided as a computer device, for example.

An input device 21 is connected to the arithmetic processing circuit 14. The input device 21 includes at least alphabet keys and a numeric key pad. Character information and numeric information are input from the input device 21 to the arithmetic processing circuit 14. The input device 21 may include a keyboard, for example. The combination of the computer device and the keyboard may be replaced by a smartphone, a cell phone terminal, a tablet PC (personal computer), or the like.

2. Motion Analysis Model

The arithmetic processing circuit 14 defines a virtual space. The virtual space is formed by a three-dimensional space. The three-dimensional space specifies a real space. As shown in FIG. 5, the three-dimensional space has an absolute reference coordinate system (global coordinate system) ΣXYZ. In the three-dimensional space, a three-dimensional motion analysis model 26 is constructed according to the absolute reference coordinate system ΣXYZ. A rod 27 of the three-dimensional motion analysis model 26 is point-constrained at a supporting point 28 (coordinate xs). The rod 27 three-dimensionally moves about the supporting point 28 as a pendulum. The location of the supporting point 28 may be shifted. Here, according to the absolute reference coordinate system ΣXYZ, the location of a center of gravity 29 of the rod 27 is specified by a coordinate xg and the location of the club head 13 c is specified by a coordinate xh.

The three-dimensional motion analysis model 26 corresponds to modelization of the golf club 13 at swing. The rod 27 of the pendulum projects the shaft 13 a of the golf club 13. The supporting point 28 of the rod 27 projects the grip 13 b. The inertial sensor 12 is fixed to the rod 27. The location of the inertial sensor 12 is specified by a coordinate xs according to the absolute reference coordinate system ΣXYZ. The inertial sensor 12 outputs acceleration signals and angular velocity signals. The accelerations from which the influence by the acceleration of gravity g is removed are specified by the acceleration signals, and the angular velocities ωx, ωy, ωz are specified by the angular velocity signals.

The arithmetic processing circuit 14 similarly fixes a local coordinate system Σs to the inertial sensor 12. The origin of the local coordinate system Σs is set to the origin of the detection axis of the inertial sensor 12. The y-axis of the local coordinate system Σs coincides with the shaft center of the shaft 13 a. The x-axis of the local coordinate system Σs coincides with the target direction A specified by the direction of the face (hitting surface). Therefore, the location lsj of the supporting point is specified by (0,lsjy,0) according to the local coordinate system Σs. Similarly, on the local coordinate system Σs, the location lsg of the center of gravity 29 is specified by (0,lsgy,0) and the location lsh of the club head 13 c is specified by (0,lshy,0).

3. Configuration of Arithmetic Processing Circuit

FIG. 6 schematically shows a configuration of the arithmetic processing circuit 14 according to one embodiment. The arithmetic processing circuit 14 includes a detection part 30 that detects rotation around the x-axis or the z-axis intersecting with the local coordinate y-axis. The detection part 30 of the embodiment includes a first detection part 31A that detects the rotation around the x-axis and a second detection part 31B that detects the rotation around the z-axis. In addition to the detection part 30, a third detection part 32 that detects the rotation around the y-axis may be provided. The first detection part 31A, the second detection part 31B, and the third detection part 32 are respectively connected to the inertial sensor 12. The output ωx is supplied from the inertial sensor 12 to the first detection part 31A. The output ωz is supplied from the inertial sensor 12 to the second detection part 31B. The output ωy is supplied from the inertial sensor 12 to the third detection part 32.

The first detection part 31A acquires the angular velocity ωx at address around the x-axis in parallel to the target line A from the inertial sensor 12. The first detection part 31A sets an initial value to the acquired angular velocity ωx0. At address, no angular velocity is generated around the x-axis, and thus, when the club stops moving at the angular velocity of “0 (zero)”, the angle “0° (zero degrees)” (=initial location) is set. The address state corresponds to a first state and the stationary state before start of swing motion.

Similarly, the second detection part 31B acquires the angular velocity ωz at address around the z-axis from the inertial sensor 12, and sets the initial value “0” in the initial location. The third detection part 32 acquires the angular velocity ωy at address around the y-axis from the inertial sensor 12, and sets the initial value “0” in the initial location.

The first detection part 31A detects a rotation angle θm (1≦m≦N) of the grip 13 b (wrists) around the x-axis from the initial location at the angle “0°” based on the output ωn (n=1, . . . , m) of the inertial sensor 12. For detection, the first detection part 31A calculates amounts of change of the rotation angle per unit time. As expressed by the following equations, the calculated amounts of change are accumulated. Here, N denotes the number of samples (the same applies to the following description).

θ₀ = 0 $\theta_{m} = {\sum\limits_{n = 1}^{m}{\omega_{n} \cdot {{dt}\left( {1 \leq m < N} \right)}}}$

As a result, the amounts of change from the initial location are calculated at each time when they are accumulated per unit time. In this manner, the rotation angle θm around the x-axis of the grip 13 b is specified according to the time axis.

Similarly, the second detection part 31B detects a rotation angle θzn (n=1, . . . , N) of the grip 13 b (wrists) around the z-axis from the initial location at the angle “0°” based on the output ωz of the inertial sensor 12. Further, the third detection part 32 detects a rotation angle θyn (n=1, . . . , N) of the grip 13 b (wrists) around the y-axis from the initial location at the angle “0°” based on the output ωy of the inertial sensor 12.

The arithmetic processing circuit 14 includes a first image data generation part 33. The first image data generation part 33 is connected to the first to third detection parts 31A, 31B, 32. The output is supplied from the first to third detection parts 31A, 31B, 32 to the first image data generation part 33. The first image data generation part 33 generates image data. In the image data, an image for visually representing the rotation angles θxn, θyn, θzn is specified. The image data of the first image data generation part 33 specifies an image representing changes of the rotation angles θxn, θyn, θzn according to the time axis. For example, the image may be a graph in which the time axis is set on the horizontal axis and the rotation angle θ is set on the vertical axis. Here, the image data may contain comparison data (comparison pattern) superimposed on the image. The comparison data represents a comparative example of the changes of the rotation angle θ. The comparison data may represent swing motion of a professional, an expert, another subject having the equal skill to the subject, or the like.

The arithmetic processing circuit 14 includes a position detection part 34. The position detection part 34 is connected to the inertial sensor 12. The output is supplied from the inertial sensor 12 to the position detection part 34. Here, the output of the inertial sensor 12 includes the accelerations respectively detected along the orthogonal three axes and the angular velocities respectively detected around the orthogonal three axes. The position detection part 34 detects the position of the golf club 13 based on the output of the inertial sensor 12. For the position detection, for example, the position detection part 34 detects the locations of the grip 13 b and the club head 13 c in motion. For the location detection, for example, the position detection part 34 calculates the acceleration of the grip 13 b according to the following equation. For acceleration calculation, the position detection part 34 specifies the location lsj of the grip 13 b according to the intrinsic local coordinate system Σs of the inertial sensor 12. For the specification, the position detection part 34 acquires location information from the memory device 16. The locations lsj of the grip 13 b are stored in the memory device 16 in advance. The location lsj of the grip 13 b may be designated via the input device 21, for example.

α_(sj)=α_(s)+{dot over (ω)}_(s) ×l _(sj)+ω_(s)×(ω_(s) ×l _(sj))+g

The position detection part 34 calculates the movement speeds of the grip 13 b based on the calculated accelerations. Here, integration processing is performed on the accelerations at preset sampling intervals dt according to the following equations.

V_(sj)(0) = 0 ${V_{sj}(t)} = {\sum\limits_{n = 1}^{t}{{\alpha_{sj}(n)} \cdot {{dt}\left( {{t = 1},\ldots \mspace{14mu},N} \right)}}}$

Further, the position detection part 34 calculates the positions of the grip 13 b based on the calculated speeds. Here, integration processing is performed on the speeds at the preset sampling intervals dt according to the following equations.

${P_{sj}(t)} = {\sum\limits_{n = 1}^{t}{{V_{sj}(n)} \cdot {{dt}\left( {{t = 1},\ldots \mspace{14mu},N} \right)}}}$

Similarly, the position detection part 34 detects the locations of the club head 13 c according to the following equations. For the location detection, the position detection part 34 specifies the locations lsh of the club head 13 c according to the intrinsic local coordinate system Σs of the inertial sensor 12. For the specification, the position detection part 34 acquires location information from the memory device 16. The locations lsh of the club head 13 c are stored in the memory device 16 in advance. The location lsh of the club head 13 c may be designated via the input device 21, for example.

$\alpha_{sh} = {\alpha_{s} + {{\overset{.}{\omega}}_{s} \times _{sh}} + {\omega_{s} \times \left( {\omega_{s} \times _{sh}} \right)} + g}$ V_(sh)(0) = 0 ${V_{sh}(t)} = {\sum\limits_{n = 1}^{t}{{\alpha_{sh}(n)} \cdot {{dt}\left( {{t = 1},\ldots \mspace{14mu},N} \right)}}}$ ${P_{sh}(t)} = {\sum\limits_{n = 1}^{t}{{V_{sh}(n)} \cdot {{dt}\left( {{t = 1},\ldots \mspace{14mu},N} \right)}}}$

The arithmetic processing circuit 14 includes a swing image data generation part 35. The swing image data generation part 35 is connected to the position detection part 34. The output of the position detection part 34 is supplied to the swing image data generation part 35. The swing image data generation part 35 specifies the movement path of the golf club 13 based on the locations of the grip 13 b and the locations of the club head 13 c calculated in the position detection part 34. An image representing the swing motion is generated based on the specified movement path. The image is output as image data from the swing image data generation part 35.

The arithmetic processing circuit 14 includes a stationary state detection part 36. The stationary state detection part 36 is connected to the inertial sensor 12. The output of the inertial sensor 12 is supplied from the inertial sensor 12 to the stationary state detection part 36. Here, the output of the inertial sensor 12 includes the accelerations respectively detected along the orthogonal three axes and the angular velocities respectively detected around the orthogonal three axes. The stationary state detection part 36 determines the stationary state of the golf club 13 based on the output of the inertial sensor 12. When the output of the inertial sensor 12 is below a threshold value, the stationary state detection part 36 determines the stationary state of the golf club 13. The stationary state of the golf club 13 represents address in swing motion. The threshold value may be set to a value that can eliminate the influence of the detection signal indicating minute vibration such as body motion. When confirming the stationary state over a predetermined period, the stationary state detection part 36 outputs a stationary state notification signal. The stationary state notification signal is sent to the first detection part 31A, the second detection part 31B, the third detection part 32, and the position detection part 34. The first to third detection parts 31A, 31B, 32 set the initial locations at the angle “0°” in response to the reception of the stationary state notification signal, and starts calculation of the rotation angles. The position detection part 34 starts detection of the position of the golf club 13 in response to the reception of the stationary state notification signal.

Here, for determination of the stationary state, the stationary state detection part 36 may refer to the tilt angle of the golf club 13. In this regard, the stationary state detection part 36 calculates the tilt angle, i.e., position of the golf club 13 based on the coordinates of the grip 13 b and the coordinates of the club head 13 c. The stationary state detection part 36 determines the position of the golf club 13 at address based on the calculated tilt angle. Whether or not the tilt angle falls within a predetermined tilt angle range is determined. The position of the golf club 13 at address is established, and then, the stationary state detection part 36 starts determination of the stationary state of the golf club 13.

The arithmetic processing circuit 14 includes an event detection part 37. The event detection part 37 is connected to the position detection part 34. The output of the position detection part 34 is supplied to the event detection part 37. The event detection part 37 specifies the event during swing motion based on the position of the golf club 13. For example, the event detection part 37 detects the axis of the grip 13 b (i.e., the axis of the shaft 13 a) provided in parallel to the ground. In this manner, halfway-back during back-swing may be specified. For example, the event detection part 37 may detect the changes of accelerations at switching from back-swing to down-swing. In this manner, top of back-swing is specified. For the detection, the event detection part 37 may acquire a reference value for comparison from the memory device 16.

The arithmetic processing circuit 14 includes a calculation part 38. The calculation part 38 is connected to the event detection part 37 and the first to third detection parts 31A, 31B, 32. The output of the event detection part 37 and the output of the first to third detection parts 31A, 31B, 32 are supplied to the calculation part 38. The calculation part 38 correlates individual events with the rotation angles θxn, θyn, θzn. The events such as halfway-back and top are correlated with the specific rotation angles θxn, θyn, θzn.

The arithmetic processing circuit 14 includes a second image data generation part 39. The second image data generation part 39 is connected to the calculation part 38. The output is supplied from the calculation part 38 to the second image data generation part 39. The second image data generation part 39 generates image data. In the image data, an image visually representing the rotation angles θxn, θyn, θzn is specified. The image data of the second image data generation part 39 specifies the image representing the rotation angles θxn, θyn, θzn with notation of the event. The image may be a pseudo circular graph in which the rotation angles θxn, θyn, θzn are specified around the center point, for example. Here, the graph may contain comparison data (comparison pattern) superimposed on the image. The comparison data represents comparative examples of the rotation angles θxn, θyn, θzn with respect to each event. The comparison data may represent the swing motion of the professional, the expert, and the other subject as described above.

The arithmetic processing circuit 14 includes a drawing part 41. The drawing part 41 is connected to the first image data generation part 33, the second image data generation part 39, and the swing image data generation part 35. The output is supplied from the first image data generation part 33, the second image data generation part 39, and the swing image data generation part 35 to the drawing part 41. The drawing part 41 draws an image representing changes of the rotation angle θn according to the time axis based on the output of the first image data generation part 33. Similarly, the drawing part 41 draws an image representing the rotation angles θxn, θyn, θzn with notation of the event based on the output of the second image data generation part 39. The drawing part 41 draws an image representing the swing motion based on the output of the swing image data generation part 35.

4. Operation of Golf Swing Analyzing Apparatus

The operation of the golf swing analyzing apparatus 11 will be briefly explained. First, golf swing of a golfer is measured. Prior to the measurement, necessary information is input from the input device 21 to the arithmetic processing circuit 14. Here, according to the three-dimensional motion analysis model 26, input of the location lsj of the supporting point 28 according to the local coordinate system Σs and a rotation matrix R0 of the initial position of the inertial sensor 12 is prompted. The input information is managed under a specific identifier, for example. The identifier may identify a specific golfer.

Prior to the measurement, the inertial sensor 12 is attached to the shaft 13 a of the golf club 13. The inertial sensor 12 is relatively displaceably fixed to the golf club 13. Here, one of the detection axes of the inertial sensor 12 is aligned with the axis of the shaft 13 a. Another one of the detection axes of the inertial sensor 12 is aligned with the hitting direction specified by the direction of the face (hitting surface).

Prior to execution of golf swing, the measurement of the inertial sensor 12 is started. At the start of motion, the inertial sensor 12 is set in predetermined location and position. These location and position correspond to those specified by the rotation matrix R0 of the initial position. The inertial sensor 12 continuously measures the accelerations and the angular velocities at specified sampling intervals. The sampling intervals define the resolution of the measurement. The detection signals of the inertial sensor 12 are sent into the arithmetic processing circuit 14 in real time. The arithmetic processing circuit 14 receives the signals specifying the output of the inertial sensor 12.

For example, the golf swing starts from address as the first state, take-back, halfway-back, top, through down-swing and impact, follow-through, to finish. The positions of the golf club 13 and the subject at the event such as halfway-back or top correspond to the second state and correspond to a dynamic state after the start of swing motion. The golf club 13 is swung. At swing, the positions of the golf club 13 and the subject change according to the time axis. The inertial sensor 12 outputs detection signals in response to the positions of the golf club 13 and the subject. Concurrently, the position detection part 34 calculates the positions of the golf club 13 according to the time axis based on the detection signals at swing motion. The swing image data generation part 35 specifies the movement path of the golf club 13 at swing motion based on the calculated positions of the golf club 13. The swing image data generation part 35 generates three-dimensional image data (e.g., polygon data) visually representing the swing motion. The drawing part 41 draws an image visually specifying the movement path 42 of the golf club 13 based on the three-dimensional image data as shown in FIG. 7, for example. In this manner, the swing motion is visually represented by the image. The drawing data is sent to the image processing circuit 18 and the image is projected on the screen of the display device 19 according to the drawing data.

For the measurement of golf swing, the subject first assumes the position of address. At the address, the subject reproduces the position at the moment of impact. As a result, the position at the moment of impact is extracted from a series of motion of “golf swing”. At the same time, the golf club 13 is held in the stationary position. The stationary state detection part 36 detects the stationary state of the golf club 13. The stationary state detection part 36 outputs the stationary state notification signal. The first to third detection parts 31A, 31B, 32 set the initial locations at the angle “0°” in response to the reception of the stationary state notification signal, and starts calculation of the rotation angles θxn, θyn, θzn. The position detection part 34 starts detection of the position of the golf club 13 in response to the reception of the stationary state notification signal.

Starting from address and during swing motion, the first to third detection parts 31A, 31B, 32 detect the rotation angles θxn, θyn, θzn at preset unit time intervals. The rotation angles θxn, θyn, θzn of the grip 13 b and the wrists are specified according to the time axis. The output signals specifying the rotation angles θxn, θyn, θzn are sent to the first image data generation part 33. The first image data generation part 33 generates two-dimensional image data specifying an image representing changes of the rotation angles θxn, θyn, θzn according to the time axis. The drawing part 41 draws the image representing changes of the rotation angles θxn, θyn, θzn according to the time axis based on the generated two-dimensional image data as shown in FIGS. 8 and 9.

Here, the subject in FIG. 8 is an amateur golfer and the subject in FIG. 9 is a professional golfer. By the representation in FIGS. 8 and 9, swings of the professional and the amateur may be compared. In the case of the professional golfer, as shown in FIG. 9, the rotation angle θyn of the arm rotation is smaller than that of the amateur golfer in FIG. 8. In contrast, the cock relative angle θxn and the hinge relative angle θzn of the professional golfer shown in FIG. 9 are larger than those of the amateur golfer in FIG. 8.

As described above, understanding of the differences in swing is facilitated by comparison of the rotation angles θxn, θyn, θzn with the comparison data, and thus, as shown in FIG. 10, comparison data 43 of a teaching pro may be drawn at the same time in addition to subject 1 and subject 2. Note that only the rotation angle θxn of the arm rotation is shown in FIG. 10, however, the comparison data may be superimposed on the other rotation angles θxn, θzn.

The event detection part 37 specifies the event during swing motion based on the output of the position detection part 34. Here, the event detection part 37 specifies halfway-back or top during back-swing. For example, the event detection part 37 correlates the lapse time from address with the event such as halfway-back or top. Thus specified halfway-back or top is output as data with a time stamp.

The output of the event detection part 37 is sent to the calculation part 38. The output signals specifying the rotation angles θxn, θyn, θzn are sent from the first to third detection parts 31A, 31B, 32 to the calculation part 38. The calculation part 38 correlates the event such as halfway-back or top with a specific rotation angle θ. The data of the rotation angle θ correlated with the event is sent to the second image data generation part 39. The second image data generation part 39 generates two-dimensional image data specifying an image representing the rotation angles θxn, θyn, θzn with notation of the event (FIGS. 11 to 13). In this regard, the second image data generation part 39 affixes “Address” or its notation number “1” to the initial location of the rotation angle θ, affixes “Halfway Back” or its notation number “2” to the location of the rotation angle θ corresponding to halfway-back, affixes “Top” or its notation number “3” to the location of the rotation angle θ corresponding to top, affixes a notation number “4” to the location of the rotation angle θ corresponding to impact, and affixes “Max” to the location in which the rotation angle θxn of the arm rotation shows the maximum value. The drawing part 41 draws images of “Address”, “Halfway back”, “Top”, “Max” or their notation numbers at the rotation angles θ based on the generated two-dimensional image data as shown in FIGS. 11 to 13, for example. In the pseudo circular graph, the initial angle “0°” is shown by “Address” and the rotation angle θ is shown clockwise or counterclockwise. In this image, as shown in FIG. 14, comparison data 44 of a teaching pro may be drawn at the same time. Note that the pseudo circular graph in FIG. 14 shows an example of the rotation angle θxn of the arm rotation, however, the comparison data may be superimposed on the pseudo circular graphs of the other rotation angles θxn, θzn.

For starting swing, the subject determines the position of the golf club 13 at impact in advance. From here, swing motion including impact is newly performed. During swing motion, the rotation angles of the grip 13 b around the axis of the grip 13 b are detected. The rotation angles θxn, θyn, θzn are visually represented on the screen of the display device 19 based on the output of the first image data generation part 33 and the output of the second image data generation part 39. In this manner, the rotation of the grip 13 b around the axis is presented to the subject. It is known that the rotations of the grip 13 b and the wrists have an effect on the direction of the hit ball after impact. The subject may improve the form of swing in response to the rotations of the grip 13 b and the wrists.

Particularly, according to the output of the first image data generation part 33, the changes of the relative angle are visually presented according to the time axis, and thus, the subject can intuitively recognize the degrees of changes and the speeds of changes. On the basis of the recognition, the subject may improve the form of swing. On the other hand, according to the output of the second image data generation part 39, the event such as address, halfway-back, or top is visually presented with respect to each relative angle, and thereby, the subject can intuitively recognize the relation between the relative angle and the event. On the basis of the recognition, the subject may improve the form of swing. The axis of the grip 13 b is directed in parallel to the ground in halfway-back, and thus, the event detection part 37 can specify the angle of the halfway-back. On the basis of the index, the subject may improve the form of swing.

In addition, in the image according to the time axis and the image of the pseudo circular graph, the swing motions of the professional and the expert are represented by comparison data. Thus, the changes of the rotation angle θ of the subject are compared with the changes of the rotation angles of the professional and the expert, and the rotation angle θ of the subject is compared with the rotation angles of the professional and the expert with respect to each event. According to the comparison, the subject may improve the form of swing.

In the inertial sensor 12, when at least the angular velocity around the axis of the shaft part of the sporting tool is detected, the rotation angle of the grip 13 b is detected. When the accelerations are respectively detected along the orthogonal three axes and the angular velocities are respectively detected along the orthogonal three axes by the inertial sensor 12, the position of the golf club 13 is detected by one inertial sensor 12.

Note that, in the above described embodiment, the individual functional blocks of the arithmetic processing circuit 14 are realized in response to the execution of the golf swing analysis software program 17. However, the individual functional blocks may be realized by hardware without software processing.

In the embodiment, in golf swing, the rotation angles of the grip 13 b and the wrists at address and at certain times during golf swing have been described, however, the rotation angles at certain two points of time during swing may be calculated. Further, not limited to golf swing, the invention may be applied to analyses of sports with swing motion using sporting tools (e.g., tennis, baseball, etc.).

As above, the embodiment has been explained in detail, however, a person skilled in the art could readily understand that many modifications may be made without substantially departing from the new matter and the advantages of the invention. Therefore, these modified examples may fall within the range of the invention. For example, in the specification and the drawings, terms described with different terms in a broader sense or synonymous sense at least once may be replaced by the different terms in any part of the specification or drawings. Further, the configurations and operations of the inertial sensor 12, the arithmetic processing circuit 14, the three-dimensional motion analysis model 26, etc. are not limited to those explained in the embodiment, but various modifications may be made. For example, the arithmetic processing circuit 14, the image processing circuit 18, and any other processing circuits used herein may be embodied by a single processing unit, such as a central processing unit (CPU), more than one processing unit, or may be embodied by one or more special purpose circuits. The processing units are not limited to CPUs, and may be provided by any other type of processing unit. Furthermore, the attachment location of the inertial sensor 12 is not limited to the shaft 13 a, but may be another location of the sporting tool or the wrist or arm of the subject depending on the detected angle. 

What is claimed is:
 1. A motion analyzing apparatus comprising an arithmetic processing circuit that calculates, within a plane orthogonal to a first direction in which a shaft part of a sporting tool extends, a rotation angle of the shaft part changing around an axis in at least one of a second direction and a third direction orthogonal to each other based on an inertial force generated when a first state of the sporting tool changes to a second state by swing motion of the sporting tool.
 2. The motion analyzing apparatus according to claim 1, wherein the first state is a state before start of the swing motion and the second state is a dynamic state of the swing motion.
 3. The motion analyzing apparatus according to claim 1, wherein the second direction is along a rotation axis at pronation or supination of a wrist of the subject holding a grip part of the sporting tool.
 4. The motion analyzing apparatus according to claim 1, wherein the third direction is along a rotation axis at ulnar flexion or radial flexion of a wrist of the subject holding a grip part of the sporting tool.
 5. The motion analyzing apparatus according to claim 1, wherein the arithmetic processing circuit calculates a relative value of the rotation angle changing around the axis in the first direction between the first state and the second state.
 6. The motion analyzing apparatus according to claim 1, wherein information of the rotation angle is output.
 7. The motion analyzing apparatus according to claim 1, wherein a change of the rotation angle is output in response to a time during swing motion of the sporting tool.
 8. The motion analyzing apparatus according to claim 6, wherein the information of the rotation angle is output with information of another rotation angle for comparison.
 9. The motion analyzing apparatus according to claim 1, further comprising an event detection part that specifies an event during swing motion based on the inertial force, wherein information of the rotation angle is correlated with the event.
 10. The motion analyzing apparatus according to claim 9, wherein the event and the information of the rotation angle are output.
 11. The motion analyzing apparatus according to claim 9, wherein the event is output with information of another rotation angle for comparison.
 12. A motion analyzing method comprising calculating, within a plane orthogonal to a first direction in which a shaft part of a sporting tool extends, a rotation angle of the shaft part changing around an axis in at least one of a second direction and a third direction orthogonal to each other based on an inertial force generated when a first state of the sporting tool changes to a second state by swing motion of the sporting tool.
 13. A non-transitory computer-readable medium storing a motion analyzing program causing a computer to execute: a procedure of calculating, within a plane orthogonal to a first direction in which a shaft part of a sporting tool extends, a rotation angle of the shaft part changing around an axis in at least one of a second direction and a third direction orthogonal to each other based on an inertial force generated when a first state of the sporting tool changes to a second state by swing motion of the sporting tool.
 14. A motion analyzing apparatus for analyzing motion of a sporting tool, comprising: an inertial sensor including an arithmetic processing circuit that calculates, within a plane orthogonal to a first direction in which a shaft part of the sporting tool extends, a first rotation angle of the shaft part changing around an axis in a second direction orthogonal to the first direction, and calculating a second rotation angle of the shaft part changing around an axis in a third direction orthogonal to the first direction and to the second direction based on an inertial force generated when a first state of the sporting tool changes to a second state by swing motion of the sporting tool.
 15. The motion analyzing apparatus according to claim 14, wherein the first state is a state before start of the swing motion and the second state is a dynamic state of the swing motion.
 16. The motion analyzing apparatus according to claim 14, wherein the second direction is along a rotation axis at pronation or supination of a wrist of the subject holding a grip part of the sporting tool.
 17. The motion analyzing apparatus according to claim 14, wherein the third direction is along a rotation axis at ulnar flexion or radial flexion of a wrist of the subject holding a grip part of the sporting tool.
 18. The motion analyzing apparatus according to claim 14, further comprising a display device configured to display the first rotation angle and the second rotation angle in association with a time of the swing motion of the sporting tool. 